The connection mentioned at the outset is a hybrid adhesive bond which is employed in the field of joining technology, more specifically in particular in the connection of construction components, preferably steel, metal or plastics hollow profiles, with uses for example in the construction of buildings, infrastructures, bridges, cranes, towers and wind turbines.
Conventional connections between construction components are usually implemented by welding, screwing or riveting. Recently, however, adhesive bonds, as are generally known in vehicle construction or in the aerospace industry, are increasingly the focus of applied research projects for this purpose in civil engineering as well. In contrast to the structural adhesive bonds in automobile construction which are implemented with thin adhesive layers and often under clean laboratory-type environmental conditions, in the building industry a thin layer adhesion cannot generally be carried out due to the unavoidable considerable manufacturing and dimensional tolerances of the joining partners. The real gap dimensions to be bridged in the building industry are often of the order of magnitude of from 3 to 15 mm and even greater. This leads to a diminishing capacity to withstand stress compared with thin layer adhesions, and it also means large quantities of adhesive are required which, when the usual quality adhesives are used, entails enormous costs. Furthermore, the adhesive bond has to be carried out in situ under sometimes adverse construction site conditions due to the structure sizes. This increases the susceptibility to defects in the adhesive bond.
It is generally known to reinforce concrete with metal or plastics structures or to cast metallic elements fully or in part into concrete and to thereby fix them in a form-locking manner. For example, in reinforced concrete construction, steel rods or steel mats have been laid in situ in the concrete for decades and have been connected in a form-locking manner as a result of the curing of the concrete. Likewise, it is generally possible to cast into concrete metallic elements such as masts, posts, abutments, bollards or other retaining means also in situ in a form-locking manner and thus to fix them in a stationary manner in the foundations or on civil engineering structures. In this respect, the metallic elements are incorporated in a matrix of concrete or mortar. It is not easily possible to transfer these known technologies to an adhesive bond, i.e. to a connection between two mutually opposite joining surfaces of two joining partners.
However, a joining method in the building industry provides casting adhesive gaps between preferably metal construction components, one of which has been inserted into the other, with a mineral binder, such as mortar, instead of with an organic adhesive. In this respect, a form-locking connection of the mortar with the joining surfaces is produced, which is commonly known by experts as a grouted joint.
By way of example, the website of SKI Schaumann & Keindorf Ingenieur-ges mbH, i.e. http://www.ski-consult.de/verbindungstechnik/grouted-joints.html, discloses (as of Nov. 26, 2014) a grouted joint connection of this type between two overlapping pipes, inserted one inside the other, in the offshore oil and gas industry, in which the joining gap, produced by the overlap region, is filled with a mortar. The joining surfaces are configured in an encircling manner corresponding to the pipe diameters. A movement of said pipes relative to one another is thereby practically only possible as a shearing movement in the radial or axial pipe orientation within the scope of the described connection. To prevent this, the joining surfaces are provided with projecting welded-on shear ribs which cause the formation of compression struts between offset, opposite shear ribs. This significantly increases in particular the bearing capacity of the connection in the longitudinal direction of the pipe. However, the connection concept not only remains form-locking, but also gives rise to pronounced stress inhomogeneities in the mortar, which results in material fatigue, particularly in the case of an alternating load. In this respect, the focus of experiments was to improve the load-bearing strength and fatigue resistance by using different filler materials.
DE 103 30 963 A1 discloses a similar configuration for a foundation for constructions, where an inner pipe is inserted inside an outer pipe, with the formation of a substantially encircling intermediate space, the intermediate space being filled at least in part with a concrete-type substance and the joining surfaces being provided with annular accumulations of material to increase the possible shear transfer.